Temperature response measurements from eucalypts give insight into the impact of Australian isoprene emissions on air quality in 2050 [post]

Kathryn M. Emmerson, Malcolm Possell, Michael J. Aspinwall, Sebastian Pfautsch, Mark G. Tjoelker
2020 unpublished
<p><strong>Abstract.</strong> Predicting future air quality in Australian cities dominated by eucalypt emissions requires an understanding of their emission potentials in a warmer climate. Here we measure the temperature response in isoprene emissions from saplings of four different Eucalyptus species grown under current and future average summertime temperature conditions. The future conditions represent a 2050 climate under Representative Concentration Pathway 8.5, with
more » ... ge daytime temperatures of 294.5 K. Ramping the temperature from 293 K to 328 K resulted in these eucalypts emitting isoprene at temperatures 4–9 K higher than default maximum emission temperature in the Model of Emissions of Gases and Aerosols from Nature (MEGAN). New basal emission rate measurements were obtained at the standard conditions of 303 K leaf temperature and 1000 μmol m<sup>−2</sup> s<sup>−1</sup> photosynthetically active radiation and converted into landscape emission factors. We applied the eucalypt temperature responses and emission factors to Australian trees within MEGAN and ran the CSIRO Chemical Transport Model for three summertime campaigns in Australia. Compared to the default model, the new temperature responses resulted in less isoprene emission in the morning and more during hot afternoons, improving the statistical fit of modelled to observed ambient isoprene. Compared to current conditions, an additional 2 ppb of isoprene is predicted in 2050 causing hourly increases up to 21 ppb of ozone and 24-hourly increases of 0.4 μg m<sup>−3</sup> of aerosol in Sydney. This forecasted increase in ozone is one fifth of the hourly Australian air quality limit and suggests anthropogenic NO<sub>x</sub> should be further reduced to maintain healthy air quality in future.</p>
doi:10.5194/acp-2020-83 fatcat:jeldrebf4vae7diajevm2dgjbu